Bone marrow transplantation is an effective therapy for an increasing number of diseases. Graft Versus Host Disease (GVHD), however, limits bone marrow transplantation to recipients with HLA-matched sibling donors. Even then, approximately half of the allogenic bone marrow transplantation recipients develop GVHD. Current therapy for GVHD is imperfect and the disease can be disfiguring and/or lethal. Thus, risk of GVHD restricts the use of bone marrow transplantation to patients with otherwise fatal diseases, such as malignancies, severe aplastic anemia, and congenital immunodeficiency states. Less than 1000 bone marrow transplantations per year are currently performed in the United States. Many other patients have diseases that might be treated by marrow cell transplantation (such as sickle cell anemia) if GVHD were not such a serious risk.
The potential benefits from expanded use of bone marrow transplantation have stimulated research on the cause and prevention of GVHD. It has been shown that donor T lymphocytes cause GVHD in animals. Removal of T lymphocytes from donor marrow inocula ("grafts") prevented the subsequent development of GVHD in mice, dogs and monkeys. Similar trials in humans with monoclonal antibodies against human T lymphocytes are now in progress. Preliminary results, however, suggest only attenuation of GVHD, not a cure. Similar results have been achieved with E-rosette and soybean lectin depletion of T lymphocytes. Another approach under investigation is the use of anti-T lymphocyte monoclonal antibodies conjugated to toxins, such as ricin.
As of yet, however, GVHD has not been prevented or cured in bone marrow recipients. A continuing need exists, therefore, for new methods of combatting Graft Versus Host Disease.
Donors of bone marrow are also faced with undesirable procedures and risks. The current procedures for harvesting bone marrow are expensive and painful. Furthermore, the current donation procedure is accompanied by the risks associated with anesthesia, analgesia, blood transfusion and possible infection. It would be desirable, therefore, to improve the current method of harvesting marrow from donors.